Science Saturday: Vitamin D might lower blood pressure

DALLAS — Vitamin D supplements significantly reduced blood
pressure in the first large controlled study of African-Americans, researchers
report in the American Heart Association journal Hypertension.

View full sizeSome promising research has shown Vitamin D might be helpful in lowering blood pressure.

In the prospective trial, a three-month regimen of daily vitamin D
increased circulating blood levels of vitamin D and resulted in a decrease in
systolic blood pressure ranging from .7 to four mmHg (depending upon the dose
given), compared with no change in participants who received a placebo.

Systolic blood pressure, the top and highest number in a reading,
is pressure in the arteries when the heart beats. Diastolic blood pressure, the
bottom and lower number, is pressure in the arteries between heart beats.

"Although this needs to be studied further, the greater prevalence
of vitamin D deficiency among African-Americans may explain in part some of the
racial disparity in blood pressure," said John P. Forman, M.D., M.Sc., lead
author of the study and Assistant Professor of Medicine in the Renal Division
and Kidney Clinical Research Institute at Brigham and Women's Hospital in
Boston, Mass.

African-Americans
have higher rates of hypertension and lower levels of circulating
25-hydroxyvitamin D (vitamin D3 or cholecalciferol) than the rest of the U.S.
population. Few studies have included enough African-Americans to determine
whether vitamin D supplements might reduce the racial disparity.

To explore this, researchers from seven major teaching hospitals
conducted a four-arm, randomized, double-blinded study of 250 black adults.
They tested blood pressure after a three-month regimen of daily vitamin D
supplementation at one of three doses, and compared the findings with a group
taking placebo vitamins:

Taking 1,000 units of vitamin D each day for three months was
associated with a .7 mm Hg decrease in systolic blood pressure.

Taking 2,000 units was linked to a 3.4 mm Hg decrease.

Taking 4,000 units netted a 4 mm Hg drop.

Participants taking placebo supplements had an average
increase of 1.7 mm Hg.

"The gains we saw were significant but modest," Forman said.

Furthermore, diastolic blood pressure didn't change in any of the
four groups.

In prospective studies, lower blood levels of 25-hydroxyvitamin D
have been independently linked with an increased risk of developing
hypertension.

"If vitamin D supplementation lowered blood pressure among
African-Americans, its widespread use could have major public health benefits,"
said Andrew T. Chan, M.D., M.P.H., co-author of the study and Assistant
Professor of Medicine in the Division of Gastroenterology at Massachusetts
General Hospital.

The study was conducted at the Dana-Farber Cancer Institute in
Boston, Mass., and was funded by the National Institutes of Health, Department
of Defense Prostate Cancer Research Program, American Society of Clinical
Oncology Career Development Award and Pharmavite LLC in Mission Hill, Calif.

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